1. Field of the Invention
The present invention relates to a method of fabricating a display device and, more particularly, to a method of fabricating a display device having a thin film transistor (TFT).
2. Description of the Related Art
A flat panel device in which each unit pixel has a unit pixel driving circuit is referred to as an active matrix display device. The unit pixel driving circuit includes at least one thin film transistor (TFT) to control current or voltage applied to a pixel electrode.
The TFT includes a semiconductor layer, a gate electrode and source and drain electrodes, and is classified according to a type of the semiconductor layer. Specifically, the TFT is referred to as a polysilicon TFT when the semiconductor layer is formed of a polysilicon layer, and referred to as an amorphous silicon TFT when the semiconductor layer is formed of an amorphous silicon layer. For the polysilicon TFT, carrier mobility in a channel region is higher than that for the amorphous silicon TFT, so that a display device having a high resolution may be implemented. In addition, the high carrier mobility of the polysilicon TFT enables a pixel portion as well as a circuit portion for driving the pixel portion to be simultaneously formed on the substrate of the display device. As described above, when a display device includes a pixel portion and a circuit portion on the same substrate, a thin film transistor in the pixel portion and a thin film transistor in the circuit portion may have different specifications from each other. However, it is challenging to form the pixel TFT and the circuit TFT to have different electrical characteristics from each other on the same substrate.